Interpretive Summary: Bacteria produce molecules in the cell called small RNAs. The plant pathogen Pseudomonas syringae pathovar tomato strain DC3000 produces a number of small RNAs however the functions of most of them are unknown. We studied the role of one small RNA in DC3000 and found that production of this small RNA in the bacterial cell is dependent upon the stage of growth and it controls the response of the bacteria to oxidative stress and heat stress. Since oxidative and heat stresses are encountered in the environment and during infection of tomato plants, this small RNA is likely to be important for its growth and survival in a number of environments, including plants.

Technical Abstract:
Bacteria contain small non-coding RNAs (ncRNAs) that are responsible for altering transcription, translation, or mRNA stability. ncRNAs are important because they regulate virulence factors and susceptibility to various stresses. Here, the regulation of a recently described ncRNA of P. syringae DC3000, P16 was investigated. We determined that RpoS regulates the expression of P16. We found that deletion of P16 results in increased sensitivity to hydrogen peroxide compared to the wild-type strain, suggesting that P16 plays a role in the bacteria’s susceptibility to oxidative stress. Additionally the P16 mutant displayed enhanced resistance to heat stress. Our findings provide new information on the regulation and role of this ncRNA in P. syringae.